The present invention relates to a roller for the pressure treatment of a fabric web.
A roller for the pressure treatment of a fabric web is known from German Patent 29 42 002 A1. In particular, FIGS. 9 through 12 of that patent show a roller which has a hollow cylinder that can rotate about an axis. A non-rotatable cross-head extends through the hollow cylinder. Lateral support elements are mounted on the cross-head. As a result of the lateral support elements, additional forces can be exerted on the hollow cylinder perpendicular to its active plane, i.e., in general, parallel to the web.
A roller for the pressure treatment of a fabric web is subject during operation not only to forces lying precisely in the active plane. Rather, forces also arise that are perpendicular to the active plane, whether as a result of the driving forces of the fabric web, or as a result of the deformation resistance of the latter, or as a result of incorrectly calculated driving power, when the roller is driven. If the driving power is set too high, it can lead, for example, to the roller tending to operate in advance contrary to the direction of motion of the fabric web, which, since the roller is generally fixedly supported at its ends, can lead to a deformation of the roller in a plane that is parallel to the web. The same applies in the case of insufficient driving power, if the web thus carries the roller along with it and deforms it in the direction of motion.
If relatively thin-walled roller tubes made of steel, or especially plastic, are used, (whose bending resistance is not very high in comparison to thick-walled rollers made of steel), all stresses perpendicular to the active plane lead especially to noticeable deformations in the roller in a plane that is perpendicular to the active plane.
A deformation-controllable roller having lateral support elements can be seen from German Patent AS 22 30 139, FIG. 9. In this roller, however, four mating rolls are arranged around the roller offset by 90xc2x0 with respect to each other. The mating rolls, along with the roller, form four roller gaps. Therefore, the deformation of a free roller parallel to a web that is moving essentially in a planar fashion is not emphasized in this context.
In the known embodiments of rollers having lateral support elements, it is true that lateral forces can be exerted on the hollow cylinder by applying a predetermined pressure in the support element. However, in these embodiments, the position of the support element of the hollow cylinder is determined as a function of the equivalence of forces and is not established geometrically. Therefore, it is not possible, using the known embodiments, to position the hollow cylinder in a plane that is perpendicular to the active plane.
The object of the present invention is to design a deflection controlled roller so that a positioning of the hollow cylinder perpendicular to the active plane is achieved.
This objective in a first aspect is achieved by a roller which has a hollow cylinder that can rotate about an axis A and that supports the working roller periphery. A non-rotatable crosshead extends through the length of the hollow cylinder, leaving all around a distance with respect to the inner circumference of the hollow cylinder. The crosshead is supported at its ends on external support pieces. A support device is arranged on the crosshead and acts radially in the active plane of the roller against the inner circumference of the hollow cylinder. The support device transmits the forces necessary for creating the line forces exerted by the roller from the crosshead to the hollow cylinder. At least one hydrostatic support element is arranged laterally on the crosshead and acts radially perpendicular to the active plane of the roller against the inner circumference of the hollow cylinder. The hydrostatic support element is hydraulically extendable against the inner circumference of the hollow cylinder and has on the exterior side an arrangement of hydrostatic bearing pockets that are open with respect to the inner circumference of the hollow cylinder. The bearing pocket arrangement of the lateral support element can be supplied in a throttle-free manner with hydraulic fluid quantity that is constant over time. A mechanical limit stop is provided for limiting the lateral extension motion of the lateral support element.
The lateral support element is hydraulically extendable. However, the extension is only possible until the limit stop is reached. In this position, the support element stops. A quantity of hydraulic fluid that is constant over time and that escapes over the edge of the bearing pockets is continually conveyed into the bearing pockets. Between this closed, circumferential edge and the inner circumference of the hollow cylinder there is a certain gap. When, as a result of a deformation perpendicular to the active plane, the inner circumference of the hollow cylinder approaches the edge of the bearing pocket arrangement, stationary with respect to the crosshead, both the gap and the escape-flow cross-section provided by it are reduced, and the pressure in the bearing pocket arrangement rises. With it, there is also an increase in the force exerted on the inner circumference of the hollow cylinder by the support element counteracting the deformation of the hollow cylinder that has occurred. In this manner, an equilibrium is achieved. In this way, care is taken that the hollow cylinder is always in a predetermined positionxe2x80x94seen from a point of view perpendicular to the active plane.
The predetermined position is determined by the position of the limit stop or stops. It is obvious that this position is selected such that in the normal case, i.e. when the hollow cylinder is not deformed perpendicular to the active plane, no forces acting to deform the hollow cylinder are exerted upon it. In the normal case, care is taken that the gap at the lateral support element amounts to roughly 0.5 mm. In the case of support elements opposite each other and perpendicular to the active plane, this gap is specified in both support elements.
This means, in normal operation, that the quantity of hydraulic fluid conveyed constantly over time to the bearing pocket arrangement can flow, in a practically pressure-free manner, into the interstitial space between the crosshead and the inner circumference of the hollow cylinder, from where it is continually drawn off. In normal operation, the lateral support elements are therefore in a practical sense not active. They only begin to carry out their function when the gap on one or the other side begins to change perpendicular to its active plane as a result of an undesirable deformation of the hollow cylinder. Then the pressure on the side having the decreasing gap rises, and a force is exerted upon the hollow cylinder in opposition to the deformation.
The length of the lateral support elements in the roller longitudinal direction amounts to roughly {fraction (1/100)} to {fraction (1/20)} of the length of the roller. In general, over the length of the roller there will be a few, e.g., three or four, given a normal roller length of 3 to 8 m, lateral support elements of this type, support elements of this type being situated opposite each other on both sides of the crosshead, assuming deformations of the hollow cylinder are possible in both directions.
As used herein the xe2x80x9cbearing pocket arrangementxe2x80x9d is taken to mean both an individual bearing pocket as well as a group of two, three, or four bearing pockets, introduced in the contact surface of the support element, which can be provided for balancing the forces on the support element.
The xe2x80x9cmooringxe2x80x9d of a hydrostatic support element at a predetermined maximum position using a mechanical limit stop is, taken by itself, known from German Patent 39 18 989 C1. However, in this context, a support element of a different type is involved, which is arranged in the active plane of the roller and aids in positioning the hollow cylinder in the effective direction in cooperation with the support elements that generate the line forces.
The mechanical limit stop can be formed by the head of a bolt fixed on the crosshead. The bolt can at the same time act to convey the constant quantity of hydraulic fluid to the bearing pocket arrangement.
One important embodiment of the present invention is characterized in that the lateral support element is mechanically connected to the part of the support device that contacts the inner circumference of the hollow cylinder. The support element with respect to the crosshead can be displaced in the active plane perpendicular to the roller gap. In particular, a retaining bracket can be mounted on the part of the support device that contacts the inner circumference of the hollow cylinder. The retaining bracket contacts a base plate of the support element. The base plate at a planar sliding surface is displaceable on a corresponding sliding surface on the crosshead parallel to the active plane perpendicular to the roller gap.
By being connected to the part of the support device contacting the inner circumference of the hollow cylinder, i.e., for example, to a corresponding hydrostatic or hydrodynamic support shoe, the respective lateral support element can be tracked such that it continually remains positioned at the center of the hollow cylinder and its force, irrespective of the deformation of the crosshead, is always exerted against the widest location of the hollow cylinder, so that no undesirable secondary components of the force arise.
In another aspect of the present invention the roller has a hollow cylinder that can rotate about an axis A. The cylinder supports the working roller periphery. A non-rotatable crosshead extends through the hollow cylinder along its length, leaving all around a distance with respect to the inner circumference of the hollow cylinder. The crosshead is supported at its ends on external support pieces. A support device is arranged on the crosshead and acts radially in the active plane of the roller against the inner circumference of the hollow cylinder. The support device transmits the forces necessary for creating the line forces exerted by the roller from the crosshead to the hollow cylinder. A detection device, emits a distance signal representing the radial distance of the inner circumference of the hollow cylinder from the active plane perpendicular to the latter. A control device processes the distance signal, and controls the drive.
In this context, it is not the exertion of a force by at least one lateral support element that is emphasized so as to counteract a deformation or displacement of the hollow cylinder perpendicular to the active plane, but rather this deformation or displacement is influenced by a corresponding controlling of the drive, such that the hollow cylinder always remains in the correct position or alignment. In principle, there is no necessity, for this purpose, for forces to be exerted against the inner circumference of the hollow cylinder perpendicular to the active plane. Thus the deviation of the position of the hollow cylinder can be detected using the detection device, and the hollow cylinder can be repositioned accordingly.
The detection device can include at least one pressure foot, arranged laterally on the crosshead and acting in a radially perpendicular manner with respect to the active plane of the roller, the pressure foot having a measuring transducer which generates the signal reflecting the displacement of the pressure foot.
In particular, the measuring transducer, can be an inductive length-measuring transducer, because measuring transducers of this type are relatively small and robust, so that they can be arranged in the space between the inner circumference of the hollow cylinder and the lateral surface of the crosshead. In designing this arrangement, the worker skilled in the art has available to him a multiplicity of possibilities.
In the preferred exemplary embodiment, there are simultaneously present in the roller at least one transverse hydrostatic support element and one detection device for the distance of the inner circumference of the hollow cylinder from the active plane of the latter, so that the control device can therefore fall back on the signal of the detection device as well as on the pressure signal of the support element, for example such that, in the event that the displacements of the hollow cylinder are not very great, the drive is influenced already by the signal of the detection device, and an increased influencing of the drive performance only occurs in response to powerful displacement forces that cause the pressure to rise steeply.
The present invention provides for the possibility of regulating the driving power of a roller driven in accordance with the present invention. For when the driving power is not precisely correct, the roller either has a tendency to run ahead of the web moving in contact with it, or, if the driving power is too small, it is carried along by the web. In both cases, forces arise acting on the roller parallel to the web, i.e., perpendicular to the active plane, and these forces lead to a deformation of the hollow cylinder, resulting in the already mentioned gap and pressure change at the bearing pockets.
According to one embodiment of the present invention, this pressure change in the bearing pockets can be used for regulating the driving power such that no forces arise perpendicular to the active plane. However, the control of the driving power can be carried out exclusively on the basis of the measured displacement of the hollow cylinder with respect to the crosshead. Both methods of control (i.e., pressure and measurement) may be used in combination.
An exemplary embodiment of the present invention is depicted in the drawings.